1. Field of the Invention
The present invention relates to a directional light-diffusing film that is mounted to a display surface of a liquid-crystal display or plasma display or the like for the purpose of preventing a reduction in frontal intensity and preventing parallax, to a method of manufacturing the above-noted directional light-diffusing film, and to a display that uses this directional light-diffusing film.
2. Description of the Related Art
In the past, in a display such as a reflective-type liquid-crystal display as noted above, a light-diffusing film was mounted for the purpose of preventing a reduction in the frontal intensity of the display screen and preventing parallax.
This light-diffusing film was, for example, a resin sheet (film) that had surface unevenness and that included a light-diffusing substance, or was a resin sheet over which a light-diffusing layer having surface unevenness and including a light-diffusing substance was provided, so as to diffuse the light exiting from the display surface.
In the above-noted types of light-diffusing films that is a resin sheet over which a light-diffusing layer having surface unevenness and including a light-diffusing substance is provided, there are film types that have extremely small surface unevenness, which mainly use the diffusion effect of internal diffusion within the light-diffusing layer.
Because a lens film also has the same type of effect as a light-diffusing film, there are cases in which it is used in the application of a light-diffusing film.
Additionally, there is a louver film that is similar to the above-noted lens film and light-diffusing film. This louver film absorbs oblique external light and has the effect of improving frontal contrast.
While the above-noted type of light-diffusing film and lens film can improve the frontal intensity and parallax by diffusion of transmitted light, the light-diffusion effect thereof increases the scattered reflections of external light, thereby causing a significant decrease in contrast, or a tendency for an image formed by pixels on the display screen to appear out of focus.
With a light-diffusing film that mainly uses internal diffusion, it is possible to reduce the reflection of external light in comparison with the usual light-diffusing film. However, with such a light-diffusing film there is an increase in the diffusion of image light, the result being the defocusing of the image is greater than with a usual light-diffusing film.
With the above noted louver film, oblique external light is absorbed, and there is the effect of improving the frontal contrast. However, because there is no effect of diffusing transmitted light, it is not possible with this type of film to achieve an improvement in intensity and parallax.